The present invention relates to an omnidirectional electronic probe indicating the fall out of balance position, particularly suitable for use in a contour measuring machine of a known type having a displaceable head to which the probe is connected. The head can be generally displaced along three orthogonal axes by suitable mechanisms in the machine, and the machine includes electric control means to which electric signals from the probe are fed.
A known probe of this type comprises substantially a pan fixed to the upper end of the rod of the probe, from which pan three pins extend outwardly, whose axes form between them angles of 120.degree.. Said three pins terminate with their other end near insulating blocks on which, at the sides of each pin and in contact with the same, three pairs of balls are disposed. Said three pairs of balls are connected electrically in series, by means of wires, so that they, in combination with the pins, provide not only a bearing, but also a mechanically controlled switch which, owing to the contact of each pin with the adjacent balls, closes in the only one stable balance position of the rod. In fact, the contact of the rod with a surface which has to be inspected causes the rod to move from the balance position, so that in consequence of the separation of at least one pin from an adjacent ball said switch is opened and an electric signal is generated which is utilized by the measuring machine.
However, the configuration and arrangement of the aforementioned elements of the probe which form the switch are not completely satisfactory from the kinematic point of view.
Moreover, during the measuring phases some disadvantages may arise. In fact, after the probe has encountered the surface to be inspected and the switch has been opened because of the displacement of the rod, and consequently a signal has been transmitted to the measuring machine, it may sometimes arise, especially for slow measurements, after a very short time, a false closure position of the switch, with an erroneous transmission of a signal to the machine. Moreover, as the probe is brought back to a position whereby the rod returns into the balance position and the switch closes, the rod effects a plurality of damped oscillations about its balance position before being stabilized, with a sequence of closures and openings of the switch, which may, of course, transmit erroneous indications to the machine.
In consideration of the foregoing, the object of the present invention is to provide an omnidirectional electronic probe which has a new configuration and arrangement of the elements forming on the whole the switch, in order to obtain a bearing of an isostatic type, so as to avoid the aforementioned imperfections.
Another object of the present invention is to provide, for such omnidirectional electronic probe, miniaturized electronic circuits which prevent the transmission of erroneous signals to the machine during the phases of measurement, in particular during the phases of opening and closure of the switch controlled by the rod of the probe, so as to avoid the disadvantages mentioned above.
A further object of the present invention is to allow a more safe and efficient utilization of the probe on completely automatic measuring machines, i.e. by transmitting to the machine such a signal as to indicate the closure or opening position of the switch.